The present invention relates to an improved construction of a lead frame for integrated circuits (IC) and a method of fabricating such the lead frame.
A lead frame for use in a glass-encapsulated IC package has a central opening and a multiplicity of leads with free inner ends. Since the inner ends are not securely supported, they tend to bend upwardly or downwardly, or laterally. The bent lead ends cannot be bonded sufficiently to a ceramic substrate coated with glass, or securely bonded to aluminum wires.
One known proposal to eliminate the above difficulties is described in U.S. Pat. No. 4,137,546 to Frusco. The disclosed lead frame has a plurality of break-off tabs integral with the inner lead ends. The break-off tabs are severed off the inner lead ends after the leads have been bonded to the substrate. However, the inner lead ends can still be bent since the break-off tabs are independently movable. Removal of the break-off tabs cannot be mechanized since they will be cut off by being bent up and down several times.